f(x, y) = sin(x + y); D is the region inside the triangle with vertices (, 0) , (, 0) and (0, ), and outside the rectangle [/2, /2] [0, /2];

2. Evaluate the integral ff sin(x + y) dA, where D is the region inside the triangle with vertices (-7,0), (7,0), and (0, 7), and outside the rectangle [-7/2, 7/2] x [0, 7/2]